Lithium carbonate production



1963 M. ARCHAMBAULT 3,112,171

LITHIUM CARBONA'IE PRODUCTION Filed Dec. 5, 1960 2 Sheets-Sheet 1 ru200C co STORAGE II 4 M i 7 f? cooums I l INSOLUBILIZING I W I N 95C j li 1 i -5 l FILTRATION l 95% lm nv roR u Maurice AACl/AMBAt/ZT BY-PRODUCTZn u co M ITTORNEY Nov. 26, 1963 F1196. Dec. 5, 1960 M. ARCHAMBAULT BSPOOUMENE 2 Sheets-Sheet -2 REACTION FILTRATION CO and H 0 N we I (:0STORAGE (:0 1 7 l -L: coouNe INSOLUBILIZING 2 and 2 u 95C A 1 1 5FILTRATION u 95c lzvvnvron 1 Maurice ARCHAMBAl/ZT BY- PRODUCT M ar (1%IrroRA/EY United States Patent 3,112,171 LITHIUM CARBONATE PRODUCTIONMaurice Archambault, Quebec, Quebec, Canada, assignor to Department ofNatural Resources of the Province of Quebec, Quebec, Quebec, CanadaFiled Dec. 5, 1960, Ser. No. 73,679 Claims priority. application GreatBritain Feb. 9, 1960 28 Claims. (Cl. 23--63) This invention relates tothe production of lithium carbonate from calcined lithium-bearingsilicates, of which beta spodumene is a preferred species.

In order to achieve a satisfactory yield of lithium values, thedecomposition of these silicates with alkali metal salts involvesspecific conditions, depending upon the particular alkali metal saltemployed. The commercial processes for producing lithium salts generallydo not act on the silicates directly with the alkali metal salts, butemploy relatively drastic preliminary steps, for example, decompositionwith sulphuric acid to form lithium sulfate and a discardable residue.The lithium sulfate is then converted to the carbonate, and then, ifdesired, to further end salts.

Recently, there has been a paper disclosure showing the treatment ofspodumene with any sodium or calcium salt which is soluble or slightlysoluble in water, to produce the corresponding lithium salt. Thatdisclosure also states that extraction can best be obtained when thereacting solution contains sodium and hydroxyl ions, or sodium, calciumand hydroxyl ions and that the latter combination is preferable. Thespecific procedure given in the disclosure employs, for treatment,calcium chloride and sodium chloride to derive lithium chloride; sodiumchloride followed by calcium hydroxide to form lithium chloride andlithium hydroxide; or sodium hydroxide and lime to form lithiumhydroxide. Where lithium carbonate is desired, the lithium hydroxideresulting from the decomposing step is gassed with carbon dioxide.

In contrast to these procedures, the applicant has now found that betaspodumene can be reacted directly with aqueous sodium carbonate, andprovided that a combination of critical conditions forming a part ofthis invention are observed, a good yield of lithium carbonate isobtained and is readily recovered by a straight-forward recoveryprocedure according to the invention. The applicant has further foundthat the addition of calcium salts in this de composing step lowers theyield of extracted lithium and complicates the subsequent treatment.

More specifically, in accordance with the invention, beta spodumene orother appropriate lithium-bearing material is first reacted in apressure vessel with from about 1 to 12 times, preferably from 1 to 6times its weight, of aqueous sodium carbonate at an elevated temperatureof at least 140 C. up to about 300 C., for time which varies from about1 minute to about 1 hour, depending on the amount of carbonate used, thespecific temperature and on the by-products desired. The amount ofcarbonate will vary depending upon the specific temperature.

This reaction results in an aqueous slurry containing lithium carbonateand sodium aluminosilicates, the composition of which may be regulated,according to the invention, by adjusting the amount of sodium carbonateused in conjunction with the specific conditions of the decomposition.The lithium salt is in good yield and in a form that can be recovered bya straight-forward procedure also forming a part of the invention, bywhich the selected by-products can also be recovered.

According to this procedure, the slurry is treated with cold water andenough carbon dioxide to saturate the resulting mixture at ambientatmosphere or super-atmospheric pressure. The total amount of water(water in slurry plus added water) should be from about 25 to about 70times the lithium oxide present in the slurry, so as to Cit "ice

dissolve the lithium values at a temperature from about 10 C. below zeroto about 40 C. above. Then the final insoluble residue is separated fromthe solution containing the bicarbonate. The solution is then heated toa temperature within the range from about 60 C. to about C. toinsolubilize the lithium carbonate and to drive off the carbon dioxideas a gas.

The applicant believes that the failure of the prior art to suggest thisrelatively straight-forward procedure, i.e. the sole use of aqueoussodium carbonate (a) to decompose spodumene and (b) to precipitatelithium carbonate is possibly due to the fact that spodumene ores andconcentrates are associated with quartz (free silica or potentialsilicic acid) which is known to react readily with a base as strong asaqueous sodium carbonate. One skilled in the art would therefore expectto encounter the following problems making the process appearimpractical: (l) the formation of water-soluble sodium silicates, andthe resulting difficulty of getting a lithiumbearing solutionsufiiciently free from impurities to permit easy or direct precipitationof a marketable lithium salt; (2) the production of lithium silicatesand of complex lithium compounds which are still less slightlywatersolubie than lithium carbonate, the consequent drawback of beingforced to use huge amount of water to dissolve these nearly insolublesalts, and subsequently the enor mous caloric expenditure required toprecipitate the lithium salt desired and to concentrate the motherliquor prior to its reuse in the circuit; (3) the formation of highlyretentive products of reaction, especially when the spodumene is reactedwith a large excess of sodium carbonate, and the resulting seriousfiltering and washing dil'liculties encountered.

These difiiculties apparently led the prior art to the use ofcombinations of sodium and calcium salts. The applicant has found thatthese combinations deteriorate the decomposing action of aqueous sodiumsalt and merely serve to complicate the process, without helping inactual extraction.

In the applicants process, in contradistinction with those of the priorart, carbon dioxide is never used to precipitate the lithium. Thefollowing functions are assigned here to carbon dioxide at the leachingstep: first. it is used to dissolve the lithium carbonate in the form ofthe more soluble bicarbonate, thus permitting the use of smaller amountsof leaching solution; second, carbon dioxide is used to convert intolithium bicarbonate any insoluble lithium silicates or complex lithiumcompounds that may have formed, while concomitantly preventing anycontaminating impurities that were part of the former lithium silicatesor complex compounds from going into solution; third, carbon dioxide isused to prevent the soluble sodium silicates that may have formed. fromcontaminating lithium-bearing solution by transforming said silicateinto soluble bicarbonate and insoluble silica. By so doing, a solutionis produced from which pure lithium carbonate can be directly andreadily obtained.

DETAILED DESCRIPTION-PROCESS The invention has been generally describedand it will now be explained in further detail by reference tosatisfactory apparatuses and procedures which are illustrated in theaccompanying drawings, in which:

FIGURE 1 is a flow-diagram which may be adopted when a low excess ofsodium carbonate is used.

FIGURE 2 is a flow-diagram which may be adopted when a large excess ofsodium carbonate is used.

Referring to FIGURE 1, a preheated mixture of comminuted beta spodumene,water and sodium carbonatethe sodium carbonate being in small excess,for example 20 percent-is fed to a pressure vessel, preferably acontinuous autoclave (step 1) and is digested under pressure at 200 C.for approximately 1 hour, during which time the mixture is thoroughlystirred. The aqueous reaction product is charged to a bicarbonatingtower (step 3) where the temperature of the slurry is lowered throughcooling and/or adding cold water or a cooled solution obtained from thefiltration step 6. This slurry is then treated with carbon dioxide gas.The amount of water or of solution, as the case may be, is addedaccording to the amount of lithium carbonate present and to thetemperature at which the treatment is effected.

The temperature of this tower is kept at about 25 C. or at roomtemperature and the progress of the bicarbonation is followed by the pHmeasurements of the solution. The solids are then separated from thesolution through filtration or by any other suitable means (step 4); thesolids are stockpiled as marketable by-product, While the solutioncontaining the extracted lithium together with the unspent sodiumcarbonate is heated (insolubilizing step 5). The insolubilizing iseffected at a temperature approaching the boiling temperature of thesolution and preferably, while stirring. This thermal treatment causesthe carbon dioxide to evolve and the lithium carbonate to precipitate.The evolved carbon dioxide is then dried (step 7) and collected in thecarbon dioxide storage tank 8. The resulting slurry is directed to afiltration or preferably to a centrifugation (step 6) where the lithiumcarbonate is separated from the solution while still hot. The lithiumcarbonate thus produced is dried and marketed, while the mother liquoris partly used at the reaction (step 1) and partly at the leaching (step3) as previously mentioned.

Referring now to FIGURE 2, when a large excess (for example, 100%), ofsodium carbonate over the stoichiometric amount required for the lithiumoxide present is used; the discharged slurry from reaction 1 isimmediately filtered (step 2) when still hot. The solution is returnedto step 1 to react with untreated spodumene while the solids are leached(step 3) with added cold water or cooled solution from step 6 andtreated with carbon dioxide at around C. This bicarbonated slurry issubsequently filtered (step 4) to separate the solids from the solution;the solution is then heated up to about 95 C., while stirring. toinsolubilize crystalline lithium carbonate (step 5) and to evolve carbondioxide gas as previously described (FIGURE 1) and the liquor is reusedfor the primary reaction (step I) or for the leaching step 3.

It is well understood that other ways of proceeding can be adopted andany modifications of these flowsheets or conditions of operation areonly good engineering.

In the drawings the thick solid line represents the How of lithium, thethin solid line-the flow of spent sodium, the chain line-the circuit ofsolutions, and the hatched linethe circuit of carbon dioxide.

STARTING MATERIALS The lithium-bearing minerals that are particularlyamenable to treatment by the applicants process are the following:

( l) Spodumene: Li O.Al O .4SiO

(3) Eucryptite: Li O.Al O .2SiO (4) Lepidolite or lithium-mica (Li,K,Na)Al (SiO (F,OH)

Before being treated, the above mentioned silicates require a calciningtreatment at temperatures of which the minima vary according to theminerals, from about 680 C. to about 980 C., to cause their crystallattice to change or their dissociation to occur.

For spodumcne. the modification is known to take place at about around870 C., and to be only a change in the crystalline structure; thiscalcined spodumene is called beta spodumene.

For petalitc, the heating to about 680 C. is known to cause itsdissociation to beta spodumene and free silica.

For cucryptite, heating to around 980 C., produces its conversion fromtrigonal structure to a new allotropic form, called the hexagonal form.

For lepidolite, heating to about 850 C., is known to cause the evolutionof its volatile elements (F and OH) and its breaking down topara-lepidolite which is a mixture of beta spodumenc, nephelitc andleucite.

BY-PRODUCTS OF TREATMENT The solid residue left after lithium values areextracted by the appiicants process is essentially constituted of one ora few of the following complex sodium silicates:

(i) An anhydrous sodium aluminosilicate, jadeite-like,

in chemical composition: (Na O.Al O .4SiO

(2) An isometric zeolite: (Na O.Al O .4SiO .xH O) (3) An anisometriczeolite: (Na O.Al O .2SiO .yH O) (4) A sodic cancrinite, approximating:

The preferential production of one or the other of these silicates ispossible-their relative production being controlled by proper adjustmentof operating conditions.

All of these residual silicates are of potential values for theindustry, aIthough to varying degrees.

THE DECOMPOSING STEP Conditions and Chemical Required In the decomposingstep, the only chemical consumed by the process is sodium carbonate (NaCO often calicd soda ash and sometimes normal carbonate. This carbonateis used with water at various temperatures. In the decomposition of thelithium-bearing silicates, the following factors are interdependent andcritical: amounts of sodium carbonate, proportions of water,temperatures and time of reaction.

As the reaction is of hydrothermal nature, relative and respectivequantities of water and sodium carbonate are considered: they vary withtime and temperature of reaction. The amount of Na CO to be added is afunction of the lithium oxide content of the lithium-bearing charge; itvaries also with the type of sodium aluminosilicate that is desired asend product. As little as one mole (106) of Na CO may be used withsuccess for each mole (30) of the Li O contained in the material to bereacted. However, a larger amount of Na CO which is required to produceanisometric sodic zeolite or sodic cancrinite will hasten the reaction;up to about 8 moles of Na CO for one mole of Li O might be employed.

The amount of water in the reacting mixture may vary within proportionsfrom 1:1 to l0:l by weight of the lithium-bearing charge. Other factorsbeing constant, a change in the amount of Water may aliect the recoveryof lithium and the composition of the end products. Water has not only aphysical or mechanical effect, but may take part in the reaction, aspreviously shown by the composition of the hydrated sodiumaluminosilicates that are formed.

In practice, the time of the reaction may be from about one minute toabout one hour, depending on the temperature and, on the excess ofreactant and on the ratio of water to the lithium-bearing material to betreated.

The pressure inside the reactor increases according to the temperatureand is practically corresponding to the water vapor pressure of thesolution. The temperature shouid range from about C. to about 300 C.,but preferred temperatures are from about 140 C. to about 250 C.

The pressure corresponding to such temperature ranges would be fromabout 50 to about 1250 p.s.i.g. for the first range, and from about 50to about 600 p.s.i.g. for the second range.

Actually, the reaction is only carried out under pressure as a means ofkeeping the water in the liquid phase,

and consequently, the pressure will vary according to other conditionsof the reaction.

As mentioned previously, four different by-products may be obtained.

When the anhydrous sodium aluminosilicatc, jadeitelike in chemicalcomposition, is the by-product desired, the beta spodumcne or thecalcined lithium-bearing silicate is contacted with sodium carbonate inan amount ranging from about 3.5 to about 7 times the weight of thelithium oxide present (i.e. approximately one to two moles of Na CO permole of Li O), in the presence of water in an amount from about 1 toabout 1.6 times the weight of the lithium-bearing material, at atemperature from about 150 C. to about 180 C., for from about 35 toabout 50 minutes.

When the isometric sodic zeolite is sought for, as a by-product, thebeta spodumene is contacted with sodium carbonate in an amount fromabout 3.5 to about 7 times the weight of the lithium oxide present, inthe presence of water in an amount from about 1.3 to about 2.3 times theweight of the lithium-bearing material, at a temperature from about 185C. to about 250 C., for from about minutes to about 60 minutes.

When anisomctric sodic zeolite is the desired byprodnet, the calcinedlithium-bearing silicate is contacted with sodium carbonate, in anamount in the range from about 7 to about 14 times the weight of thelithium oxide present (i.e. approximately two to four moles of Na CO permole of Li O), in the presence of water in an amount from about 1.3 toabout 2 times the weight of the lithium-bearing material, at atemperature from about 140 C. to about 175 C., and for from about 5minutes to about 60 minutes.

When sodic cancrinite is sought for, the beta spodumene is contactedwith sodium carbonate, in an amount from about 14 to about 29 times theweight of the lithium oxide present, in the presence of Water, in anamount from about 2.0 to about 7 times the weight of the lithiumbearingmaterial, at a temperature within the range from about 185 C. to about200 C., and for from about 1 minute to about 10 minutes.

When anisometric sodic zeolite and sodic cancrinite are formed, there isenough concomitant production of alkali metal salts of silicic acids tofavour side reactions that would render the filtration very difficultand the extraction of the lithium values practically impossible, if theleaching solution was not a saturated aqueous carbon dioxide solution.

Considering the matter from a sodium carbonate consumption standpointonly, it seems that, generally, the most desirable by-product to aim atis the isometric zeolite. However, certain conditions may be met wherethe other by-products would be advantageously produced.

When isometric zeolite is the desired by-product, the optimum conditionsare generally met with an amount of sodium carbonate 10 to 70% in excessover the theoretical amount required, the temperature being at about 200C., for an amount of water 1.6 times the amount of the material chargedin the autoclaves, with a time of reaction not over one hour.

Calcined lepidolite, petalite and eucryptite would behave essentiallylike beta spodumene, giving the same reaction products as thosementioned above.

LEACHING AND INSOLUBILIZING The solubilizing of the lithium values isadvantageously performed at room or colder temperature with cold watersaturated with carbon dioxide or with a cooled unsaturated Li COsolution (from a previous operation) through which carbon dioxide gas isdiffusing.

The amount of carbon dioxide circulated at the leaching step variesbasically according to the temperature, the pressure, the strength andthe volume of the leaching solution, in a manner known to those skilledin the art.

The lower the temperature, the greater the solubility of the lithiumbicarbonate thus formed. The greater the carbon dioxide concentration inthe leach solution, the faster is the leaching and the smaller is theamount of water required for solubilizing the lithium values.

For example, when the leaching water is kept saturated with carbondioxide at atmospheric pressure, the amount required for solubilizingthe lithium values is in the range from about to about 70 times theweight of the lithium oxide contained in the charge, for a temperaturefrom about 0 C. to about C.

On the other hand, when the leaching water is kept saturated with carbondioxide at a pressure of about 150 p.s.i.g. the amount required is fromabout 25 to about times the weight of the lithium oxide contained in thecharge, for a temperature from about 10 C. below zero to about 20 C.above.

In practice, the whole product of the primary reaction or the solidsfrom said product is diluted with water or with the mother liquorobtained after the Li- CO insolubilizing step. Carbon dioxide isdiffused through the slurry, at ambient atmosphere or atsuperatmospheric pressure, the excess CO being collected andrecirculated.

After its separation from the solid residue, the pregnant solution iswarmed up, thereby causing the formation of solid lithium carbonate,which was preceded by evolution of carbon dioxide gas, which iscollected and returned to the process for leaching new lithium carbonatefrom the autoclave reaction product. Any temperature between about C.and about 100 C. is suitable for satisfactory Li CO insolubilisation. Ofcourse, the higher the temperature, the faster the insolubilizing butthe finer the size of the lithium carbonate crystals.

Instead of heating the solution to insolubilize the lithium carbonate,physical means, such as beating, ultrasonic irradiation, and vacuum maybe resorted to or used jointly. This applies especially when leaching isdone at low temperature and under pressure of C0 The applicant has foundthat, even if the Li CO formed in the autoclave would be expected toprecipitate, contrarily to this expectation, no trouble of any kind suchas scaling, caking, pipe plugging, etc. has occurred either in theautoclave or any parts of the complete system.

For the purpose of giving further details to illustrate the invention,the applicant furnishes the following examples of preferred procedures.All parts mentioned in the examples are by weight.

EXAMPLE 1 One hundred parts of calcined or beta spodumene concentrateanalysing 5.25% Li O (corresponding to a mixture of about spodumene, 15%quartz and 15% feldspars), together with 29 parts of Na CO (70% excess)and 120 parts of water were treated within an autoclave. The temperatureof the reaction was 200 C. and the time: one hour. After the reaction,the mixture from the autoclave was filtered and the mother liquorreturned to the process (cf. FIGURE 2, steps 1 and 2). Then the solidwas leached at 25 C. with 340 parts of a cooled aqueous solution,previously saturated with Li CO at around C., through this slurry CO wascirculated; this leaching operation lasted one hour at 25 C. (FIGURE 2,step 3). The solution was separated by filtration from the solid andthen heated to evolve CO gas and insolubilize Li CO Analysis of thelithium oxide in the residue was found to be 0.32%, which means anextraction yield of about 94%. The by-product was essentially anisometric sodic zeolite, i.e. an hydrated sodium aluminosilicate.

EXAMPLE 2 parts of same calcined concentrate as in Example 1 werecharged into an autoclave with 18 parts of Na CO (i.e. 5% under thestoichiometric amount required) and parts of water. The temperature wasraised up to 245 C., corresponding to a pressure of about 500 p.s.i. andmaintained there for 15 minutes. After treatment in the autoclave, theslurry was diluted with 350 parts of a cooled aqueous Li CO solutionpreviously saturated at around 95 C., and then leached at around 25 C.,for one hour, while bubbling carbon dioxide gas through the leachingsolution. After filtration, the solution was heated to about 95 C.,causing the evolution of CO gas and the formation of crystalline Li COwhich was recovered by filtration to the extent of 91.5% of the lithiumcharged in the autoclave. The residue was of the same zeolitic nature asin previous example.

EXAMPLE 3 One hundred parts of calcined spodumene concentrate containing4.5% M (and corresponding to a mixture of about 60% spodumene, 25%feldspars and 15% quartz) were reacted in a pressure vessel with 21parts of Na CO (30% excess) and 135 parts of water. The mixture washeated to around 235 C., or 400 p.s.i. and held there for 15 minutes.Then the temperature was lowered and the pulp flushed out at pressure ofabout 100 p.s.i. The mixture from the autoclave was leached at roomtemperature for one hour with 260 parts of cold aqueous Li CO solutionfrom a previous precipitation and under a current of C0 The slurry wasthen filtered and the solution heated to recover CO as a gas and Li COas a solid. Lithium recovery was 92.5%. The analysis of the lithiumcarbonate as obtained on the filter, without any washing gave:

Here again, the solid residue has shown to be essentially an isometricsodic zeolite of the same nature as in previous examples.

EXAMPLE 4 Over two dozen complete consecutive cyclings were effected inaccordance with the fiowsheet of the process as on FIGURE 1. Thosereactions lasted for one hour and were made at 200 C., with 10% excessof Na cO and 1.6 parts of water for 1 part of calcined spodumeneconcentrate. Lithium recoveries run between 92 and 94% while the Li COobtained was always over 99% pure. The solid residues obtained asby-products were all the time isometric sodic zeolite.

EXAM PLE 5 100 parts of the same concentrate as in Example 3 were heatedin an autoclave with 79 parts of sodium carbonate (Na CO 400% excess)and 200 parts of water at 160 C. for thirty minutes. The producttherefrom was leached with water plus CO at room temperature. Afterleaching and filtration the obtained insoluble residue contained 0.40%lithium oxide which means an extraction yield of 91%. This residue wasmostly an anisometric sodic zeolite.

EXAMPLE 6 100 parts of the same concentrate as in Example 3 were heatedin a pressure vessel with 127 parts of sodium carbonate (Na CO 700%excess) and 200 parts of water at 200 C. for about 1 minute. The producttherefrom was leached with water and CO at room temperature. Afterleaching and filtration the obtained insoluble residue contained 0.00%lithium oxide which means a yield of 100%. This residue was mostly asodic cancrinite.

EXAMPLE 7 A lepidolite concentrate ground to pass a 150 mesh screen wascalcined at 930 C. One hundred parts of this calcined lepidolite wascontacted for 1 hour at 200 C. in an autoclave together with 24 parts ofsodium carbonate and 160 parts of Water. The leaching of the reactionproduct was performed at room temperature with 200 parts of watersaturated with carbon dioxide. lithium extraction yield was The EXAMPLE1 One hundred parts of a concentrate similar to the one used for Example3 were heated for 1 hour at 200 C. in a pressure vessel with 7.9 partsof sodium carbonate plus 7.4 parts of calcium carbonate and 160 parts ofwater. Each salt added was in an amount representing 50% of thestoichiometric amount required for the Li O present. After reaction, theproduct was leached, at around 25 C., with an amount of water in excessover that required for complete solubilization of the lithium carbonateformed. The lithium recovery was 58%. This result indicates that theaddition of calcium carbonate does not improve the efficiency of sodiumcarbonate. In the solid residue (an isometric sodic zeolite), no newlyformed albite or anorthite was detected.

EXAMPLE 2 One hundred parts of the concentrate used in the precedingexample were agitated for 1 hour at 200 C. in a pressure vessel with15.9 parts of sodium carbonate plus 11 parts of calcium hydroxide and160 parts of water. The sodium and calcium salts in this case were addedapproximately in equimolecular proportions, each salt being present instoichiometric amounts for the lithium of the charge. After reaction,the slurry was filtered to remove the mother liquor and the solidmaterial was leached with water as follows: a first leaching waseffected for 50 minutes at room temperature, while stirring, with 900parts of water; this way, 33% of the lithium was extracted. A secondleaching performed with 2000 parts of water at room temperature for 50minutes and while stirring increased the above extraction by only 2%.Both leaching tests resulted in slurries which were very difficult tofilter. In the solid residue, no newly formed albite or anorthite wasdetected.

The applicant claims:

1. A process for extracting lithium values from a cal cinedlithium-bearing silicate, comprising reacting said silicatehydrothermically with water and sodium carbonate in a total amount lessthan about 12 times the weight of said calcined lithium-bearingsilicate, said carbonate being present in an amount of at least about 1mole of sodium carbonate per mole of lithium oxide to the point wheresubstantially all the lithium in the silicate has been converteddirectly to the carbonate thereby producing a mixture containing solidlithium carbonate and sodium aluminosilicate, and separating the lithiumcarbonate from the sodium aluminosilicate.

2. A process, as defined in claim 1, in which the water and sodiumcarbonate are employed in a total amount of less than about 6 times theweight of the calcined lithiumbearing silicate.

3. A process, as defined in claim 1, in which the reaction is carriedout at a temperature within the range from about C. to about 300 C. andthe Water and sodium carbonate are present in a total amount of lessthan about 6 times the weight of the calcined lithium-bearing silicate.

4. A process, as defined in claim 1, in which the calcinedlithium-bearing silicate is beta spodumene.

5. A process, as defined in claim 1, wherein the lithiumbearing silicateis a mineral selected from the group consisting of spodumene, petalite,eucryptite and lepidolite, which have been calcined to transformationtemperature.

6. A process for extracting lithium carbonate from calcinedlithium-bearing silicate, comprising, reacting said silicate at atemperature in the range from about 140 C. to about 300 C. with fromabout 1 to about 12 times the weight of said silicate of aqueous sodiumcarbonate, the amount of water present being within the range of fromabout 1 to about 7 times the weight of the lithiumbearing silicate toproduce a mixture containing lithium carbonate and sodiumaluminosilicate, and separating the lithium carbonate from thealuminosilicate.

7. A process for extracting lithium carbonate from calcinedlithium-bearing silicate, comprising, reacting the silicate underpressure and at a temperature within the range from about 150 C. toabout 180 C. with sodium carbonate in amount from about 3.5 to about 7times the weight of the lithium oxide present in the starting silicateand in the presence of water in an amount from about 1 to about 1.6times the weight of the silicate, for a time from about 35 minutes toabout 50 minutes, thereby producing a mixture containing lithiumcarbonate and an anhydrous sodium aluminosilicate, and separating thelithium carbonate from the aluminosilicate.

8. A process for extracting lithium carbonate from calcinedlithium'bearing silicate, comprising, reacting the silicate underpressure and at a temperature within the range from about 185 C. toabout 250 C. with sodium carbonate in amount from about 3.5 to about 7times the weight of the lithium oxide present in the lithiumbearingsilicate, in the presence of water in an amount from about 1.3 to about2.3 times the weight of the silicate, for a time from about 10 minutesto about 60 minutes, thereby producing a mixture containing lithiumcarbonate and isometric sodic zeolite and separating the lithiumcarbonate from the isometric sodic zeolite.

9. A process for extracting lithium carbonate from calcinedlithium-bearing silicate, comprising, reacting the silicate underpressure and at a temperature within the range from about 140 C. toabout 175 C. with sodium carbonate in amount from about 7 to about 14times the weight of the lithium oxide present in a solution containingwater in an amount from about 1.3 to about 2.0 times the weight of thesilicate, for a time from about minutes to about 60 minutes, therebyproducing a mixture containing lithium carbonate and anisometric sodiczeolite and separating the lithium carbonate from the anisometric sodiczeolite.

10. A process for extracting lithium carbonate from calcinedlithium-bearing silicate, comprising, reacting the silicate underpressure and at a temperature within the range from about 185 C. toabout 200 C. with sodium carbonate in amount from about 14 to about 29times the weight of the lithium oxide present in a solution containingwater in an amount from about 2.0 to about 7 times the weight of thesilicate, for a time from about 1 minute to about 5 minutes, therebyproducing a mixture containing lithium carbonate and sodic cancriniteand separating the lithium carbonate from the sodic cancrinite.

11. A process for producing lithium carbonate from calcinedlithium-bearing silicate, comprising, reacting said silicate underpressure with aqueous sodium carbonate in an amout exceeding thestoichiometric proportion by not more than about 100 percent, the waterbeing in an amount from about 1 to about 2.3 times the weight of thelithium-bearing silicate, at a temperature from about 140 C. to about250 C., for from about 5 minutes to about 1 hour, to produce a mixturecontaining lithium carbonate and a sodium aluminosilicate selected fromthe group consisting of isometric sodic zeolite and a sodic compoundhaving the chemical composition of jadeite and separating the lithiumcarbonate from the sodium aluminosilicate.

12. A process for producing lithium carbonate from calcinedlithium-bearing silicate, comprising, reacting said silicate underpressure at a temperature from about 140 C. to about 200 C. with fromabout 2 to about 12 times the weight of said silicate of water andsodium carbonate in which the carbonate is present in an amount fromabout 7 to about 29 times the weight of the lithium oxide present in thelithium-bearing silicate, for from about 1 minute to about 60 minutesproducing thereby a mixture containing lithium carbonate and a sodiumaluminosili- 10 cate selected from the group consisting of anisometricsodic Zeolite and sodic cancrinite and separating the lithium carbonatefrom the sodium aluminosilicate.

13. A process, as defined in claim 7, in which the calcinedlithium-bearing silicate is beta spodumene.

14. A process, as defined in claim 7, in which the lithium-bearingsilicate is a mineral selected from the group consisting of spodumcne,petalite, cucryptite and lepidolite which have been calcined totransformation temperature.

15. A process, as defined in claim 10 in which the calcinedlithium-bearing silicate is beta spodumene.

16. A process, as defined in claim 10, in which the lithium-bearingsilicate is a mineral selected from the group consisting of spodumene,petalite, eucryptite and lepidolite which have been calcined totransformation temperature.

17. A process for extracting lithium values from a calcinedlithium-bearing silicate, comprising, reacting said silicate at atemperature within the range from about C. to about 300 C. with sodiumcarbonate in an amount of at least about one mole per mole of lithiumoxide present in the silicate and in the presence of water in an amountnot more than about seven times the weight of the lithium-bearingsilicate to produce a mixture containing lithium carbonate and a sodiumaluminosilicate, cooling the mixture, subjecting the cooled mixture tothe action of carbon dioxide to solubilize the lithium, and separatingthe resulting lithium solution from the remaining solid residue.

18. A process, as defined in claim 17, in which the mixture is cooled toa temperature from about 10 C. below zero to about 20 C. above zero, thepressure of the carbon dioxide treatment is within the range up to aboutp.s.i.g. the amount of solution is within the range from about 25 toabout 50 times the weight of the lithium oxide present in thelithium-bearing charge.

19. A process for extracting lithium carbonate from calcinedlithium'bearing silicate, comprising, reacting said silicate at atemperature in the range from about 140 C. to about 300 C. with fromabout 1 to about 12 times the weight of said silicate of aqueous sodiumcarbonate, the amount of water present not exceeding seven times theweight of the lithium-bearing silicate producing thereby a mixturecontaining lithium carbonate and sodium aluminosilicate, cooling themixture to a temperature from about 10 C. below zero to about 20 C.above zero treating at said temperature the cooled mixture with aqueouscarbon dioxide at a pressure within the range up to 150 p.s.i.g., theresulting lithium solution being in an amount from about 25 to about 50times the weight of the lithium oxide present in the lithium-bearingcharge.

20. A process for extracting lithium carbonate from calcinedlithium-bearing silicate, comprising, reacting said silicate at atemperature in the range from about 140 C. to about 300 C. with fromabout 1 to about 12 times the weight of said silicate of aqueous sodiumcarbonate, the amount of water present not exceeding seven times theWeight of the lithium-bearing silicate producing thereby a mixturecontaining lithium carbonate and sodium aluminosilicate, cooling themixture, subjecting the cooled mixture to the action of carbon dioxideunder pressure to form and dissolve lithium bicarbonate, and separatingthe resulting lithium bicarbonate solution from the solid residue.

21. A process for extracting lithium from calcined lithium-bearingsilicate comprising reacting said silicate under pressure andhydrothermal conditions with aqueous sodium carbonate in a weight ratioof about 3.5 to 29 times the weight of the lithium oxide present in thesilicate, water being present in an amount not exceeding seven times theweight of the silicate, thereby to produce a mixture containing hotwater-insoluble lithium carbonate and sodium aluminosilicate, coolingthe mixture, subjecting the cooled mixture to the action of carbondioxide to form lithium bicarbonate and to leach the same, thenecoinposing the lithium bicarbonate solution by physical means so as tocause evolution of carbon dioxide and insolubilization of the lithiumcarbonate, separating the lithium carbonate from the mother liquor andrecycling the latter to the process, and returning the carbon dioxide tothe leaching step.

22. A process for extracting lithium from calcined lithium-bearingsilicate comprising reacting said silicate under pressure andhydrothermic conditions with aqueous sodium carbonate in a weight ratioof about 3.5 to 29 times the weight of the lithium oxide present in thesilicate, water being present in an amount not exceeding seven times theweight of the silicate, to produce an aqueous liquor containing solidlithium carbonate and solid sodium aluminosilicate, separating thesolids from the hot mother liquor and returning the latter to theprocess, adding water to the solid residue in an amount from about 35 toabout 70 times the weight of the lithium oxide contained in the charge,saturating the resulting mixture with carbon dioxide at a temperaturefrom about C. to about 40 C. thereby to form lithium bicarbonate and toleach the same, separating the leached solid residue from the lithiumbicarbonate solution, heating the solution to a temperature within therange from about 60 C. to about 100 C. to drive off carbon dioxide andto insolubilize crystalline lithium carbonate, recovering said carbonatefrom the mother liquor and returning the latter to the process, andrecycling the carbon dioxide to the leaching step.

23. A process for extracting lithium from calcined lithium-bearingsilicate comprising reacting said silicate under pressure andhydrothermal conditions with water and sodium carbonate in a weightratio of about 3.5 to 29 times the weight of the lithium oxide presentin the silicate, water being present in an amount not exceeding seventimes the weight of the silicate, to produce a mixture containing hotwater-insoluble lithium carbonate and sodium aluminosilicate, coolingthe mixture, adding water to the mixture in an amount from about 35 toabout 70 times the weight of the lithium oxide of the charge, saturatingthe resulting mixture with carbon dioxide at a temperature from about 0C. to about 40 C. thereby to form lithium bicarbonate and to leach thesame, separating the leached solid residue from the lithium bicarbonatesolution, heating the solution to a temperature within the range fromabout 60 C. to about 100 C. to drive off carbon dioxide and toinsolubilize crystalline lithium carbonate, recovering the lithiumcarbonate from the mother liquor and returning the latter to theprocess, and recycling the carbon dioxide to the leaching step.

24. A continuous cyclic process for producing lithium carbonate and asodium aluminosilicate directly from calcined lithium-bearing silicate,which comprises the steps of continuously decomposing lithium-bearingsilicate by contact with aqueous sodium carbonate in a Weight ratio ofabout 3.5 to 29 times the weight of the lithium oxide present in thesilicate, water being present in an amount not exceeding seven times theweight of the silicate, thereby to form a mixture containing hot-waterinsoluble lithium carbonate and a sodium aluminosilicate, cooling themixture, leaching said cooled mixture with aqueous carbon dioxide toform a lithium bicarbonate solution containing a solid aluminosilicateresidue, separating the solid residue from the solution, insolubilizingthe lithium content of the solution by heating and agitating thesolution to drive off carbon dioxide gas and to reform crystallinelithium carbonate, recovering the solid lithium carbonate from themother liquor, returning the mother liquor to the process and recyclingthe carbon dioxide to the leaching step.

25. A cyclic process for producing lithium carbonate and sodiumaluminosilicate directly from calcined lithiumbearing silicate whichcomprises the steps of:

(a) decomposing said silicate at a temperature in the range from aboutC. to about 300 C., under pressure with from about 1 to about 12 timesthe weight of said silicate of water and sodium carbonate, said saltbeing in an amount from about 3.5 to about 29 times the weight of thelithium oxide present in the silicate, in the presence of water in anamount from about 1 to about 10 times the weight of the silicate, andfor from about 1 minute to about 1 hour to form a hot mixture containingsolid lithium carbonate and sodium aluminosilicate by-product;

(b) cooling said mixture;

(c) leaching the cooled mixture at a temperature from about 10 C. belowzero to about 40 C. above with aqueous carbon dioxide at at leastatmospheric pressure;

(d) separating the leached solid residue from the lithiumbicarbonate-bearing solution;

(6) insolubilizing the lithium bicarbonate solution obtained in theleaching step by heating and agitating said solution to drive off carbondioxide gas;

(I) separating resultant crystalline lithium carbonate from the motherliquor and returning the latter to the process;

(g) recovering separately lithium carbonate and sodium aluminosilicate;and

(/1) recycling to the leaching step the carbon dioxide driven oii in theinsoluoilizing step.

26. A process for solubilizing and purifying lithium carbonate from amixture thereot with sodium aluminosilicate, comprising, subjecting saidmixture in cold aqueous conditions to the action of carbon dioxidethereby to leach lithium and separating the lithium solution from theremaining solid residue.

27. A process, as defined in claim 26, in which the leaching is carriedout under pressure at a temperature within the range from about 10 C.below zero to about 20 C. above zero, and the carbon dioxide pressure ismaintained within the range up to about p.s.i.g.

28. A process, as defined in claim 26, in which the amount of aqueouscarbon dioxide is within the range from about 25 to about 50 times theweight of the lithium oxide present in the lithium-bearing charge.

References Cited in the file of this patent UNiTED STATES PATENTS2,413,644 Nicholson Dec. 31, 1946 2,924,507 Peterson Feb. 9, 1960FOREIGN PATENTS 596,302 Canada Apr. 19, 1960

1. A PROCESS FOR EXTACTING LITHIUM VALUES FROM A CALCINEDLITHIUM-BEARING SILICATE, COMPRISNG RACTING SAID SILICATEHYDROTHERMICALLY WITH WATER AND SODIUM CARBONATE IN A TOTAL AMOUNT LESSTHAN ABOUT 12 TIMES THE WEIGHT OF SAID CALCINED LITHIUM-BEARINGSILICATE, SAID CARBONATE BEING PRESENT IN AN AMOUNT OF AT LEAST ABOUT 1MOLE OF SODIUM CARBONATE PER MOLE OF LITHIUM OXIDE TO THE POINT WHERESUBSTANTIALLY ALL THE LITHIUM IN THE SILICATE HAS BEEN CONVERTEDDIRECTLY TO THE CARBONATE THEREBY PRODUCING A MIXTURE CONTAINING SOLIDLITHIUM CARBONATE AND SODIUMALUMINOSILICATE, AND SEPARATING THE LITHIUMCARBONATE FROM THE SODIUM ALUMINOSILICATE.